The role of marine reserves in achieving sustainable fisheries

Abstract

Many fishery management tools currently in use have conservation value. They are designed to maintain stocks of commercially important species above target levels. However, their limitations are evident from continuing declines in fish stocks throughout the world. We make the case that to reverse fishery declines, safeguard marine life and sustain ecosystem processes, extensive marine reserves that are off limits to fishing must become part of the management strategy. Marine reserves should be incorporated into modern fishery management because they can achieve many things that conventional tools cannot. Only complete and permanent protection from fishing can protect the most sensitive habitats and vulnerable species. Only reserves will allow the development of natural, extended age structures of target species, maintain their genetic variability and prevent deleterious evolutionary change from the effects of fishing. Species with natural age structures will sustain higher rates of reproduction and will be more resilient to environmental variability. Higher stock levels maintained by reserves will provide insurance against management failure, including risk-prone quota setting, provided the broader conservation role of reserves is firmly established and legislatively protected. Fishery management measures outside protected areas are necessary to complement the protection offered by marine reserves, but cannot substitute for it.

Figure 1

Beverton–Holt style stock-recruitment relationship showing the range of variation in stock sizes in an unfished system, in a system with marine reserves and in a system where there are no refuges from exploitation. Marine reserves can help sustain maximal levels of recruitment by keeping stock sizes above levels at which recruitment limitation occurs. Theoretical work suggests that this mechanism leads to more stable and predictable catches.